There's very little in our anatomy that has — or had — no purpose whatsoever.

While there are a few things that might seem useless now, they exist because our ancestors once needed these features.

The appendix isn't completely useless — recent research shows it might help harbor good bacteria that fight infections.

Scientists have recently discovered that the interstitium, or the tissue surrounding our organs previously thought of as unremarkable, might actually be protective.

As the Ancient Greeks used to say, "Know Thyself." It probably was meant a little more philosophically that we're choosing to interpret it, but learning about how your body is put together and why is some seriously fun stuff.

We've all marveled at our fingers and toes, wrinkling into prunes in the bath. We've all stared at that weird fleshy appendage hanging down in the back of our throats.

We've all known someone — or been that someone — with an emergency appendectomy. "It's fine," they say, "the appendix is completely useless anyway."

But our bodies are amazing machines, and, while we may not need some of its features any more, there's very little in our anatomies with no purpose whatsoever.

We don't know why we have them - but evolutionary biologist Neil Shubin of the University of Chicago and the Field Museum of Natural History has hypothesized that they're an evolutionary remnant of fish gills.

They conducted experiments and found that underwater objects were manipulated much more adroitly by wrinkled fingers than unwrinkled fingers - suggesting that the feature exists to give us improved grip in both handling objects and walking when wet surfaces are involved.

Makes sense, doesn't it?

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Junk DNA

FILE PHOTO: A DNA double helix is seen in an undated artist's illustration released by the National Human Genome Research Institute to Reuters
Thomson Reuters

We have a lot of DNA in our body that, until recently, didn't really seem to do anything.

It doesn't create proteins, and it seems to make us more susceptible to damage and disease - but it makes up a significant part of our genome. If it wasn't somehow beneficial, evolution would have at least started phasing out this so-called "junk DNA," but that hasn't happened.

Recently, researchers may have figured out what it's for - it plays a critical role in holding out genome together by ensuring that chromosomes bundle correctly inside the nuclei if our cells. Without that function, cells die - so it seems like "junk" DNA is not so junky after all.

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"Useless" immune cells

We have these immune cells in our bodies that nobody could figure out what they were for.

It was a real head-scratcher, because these "silenced" lymphocytes are present in our bodies in large numbers and only seemed to emerge to attack the body in autoimmune diseases. It looks like a liability, right?

Gut bacteria

In recent years, research has found that the microbes that live inside of us, especially our intestines (our microbiome), are symbiotic - and they have far more of an effect on our lives than we realized.

Interstitium

Neil Theise, MD, and co-author of study by group of scientists who discovered “interstitium," looks at slides.
Elly Park/Reuters

Turns out we may have an organ wrapped around our other organs, and it's been hiding in plain sight for all this time. The newly classified organ is called the interstitium, and previously scientists had just thought it was relatively unremarkable, relatively solid tissue to fill the space between our organs.

It's actually filled with fluid, supported by a collagen lattice, and it helps protect our organs from external shocks as we move around, much like air cushions in running shoes.

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The pink bit in your eye

If you look in the mirror, you'll see a little pink bit of conjunctival tissue in the corner of your eye. This is called the plica semilunaris, and these days its primary function is to help with tear drainage and eyeball mobility.

But once upon a time it was a nictitating membrane - what we call a third eyelid, a translucent eyelid that can be drawn over the eye to keep it moist and protected while maintaining a measure of vision.

If you have a cat or a dog, you may have seen their third eyelid while they're sleeping. Humans and most other primates don't need this feature any more, so it evolved away a long time ago - but we still have that vestigial lump of tissue.